Posted
by
Soulskill
on Wednesday October 21, 2015 @10:55AM
from the first-prize-to-mark-watney dept.

schwit1 writes: NASA has picked the three winners in a design contest for 3D-printed habitats that could help future astronauts live on Mars. The $25,000 first prize in NASA's 3D-Printed Habitat Challenge Design Competition went to Team Space Exploration Architecture and Clouds Architecture Office for the 'Mars Ice House' design, which looks like a translucent, smooth-edged pyramid. That pyramid would be built of Martian ice and serve as a radiation shield, protecting the lander habitat and gardens inside it, team members said. The Mars Ice House's ribbed interiors and exteriors glow with diurnally determined hues at various times of sol (Martian day). In one illustration from the team's proposal, the outer shell is washed in Mars’ inky blue sunset, and in another it looks like it was dipped in the tea-tinged pink of the high noon on Mars.

The interior won't stay at a fixed temperature. Heat will build up in your insulated box. Humans and human activity tend to generate heat at a far higher temperature than is necessary to melt ice (we'll assume they're pressurizing the fucking thing and adding an Earth-like atmosphere, if they're not, then it's sublimation at a much lower temperature).

Insulation does not regulate temperature. A closed box needs to have active temperature regulation for long term use.

Insulation does not regulate temperature. A closed box needs to have active temperature regulation for long term use.

You do have active temperature regulation. It's called "thousands of square meters of external surface area convecting with the atmosphere and radiating into space". It's a well pretty known thing that things on Mars tend to get cold. Usually there's far more challenge to have them not get too cold than to cool them down - hence, even Mars missions that don't use RTGs still tend to use smaller radiothermal heaters.

Any temperature gradient moving across the ice (in the above, -50C to -60C) means heat loss. The greater the gradient, the faster the heat loss - if you wanted more heat loss you could reduce the insulation and bump the inside of the ice's temperature up to say -10C and get a 50-degree delta-T instead of a 10-degree delta-T and thus 5x higher heat flow. But again, with this large of a structure, "getting too hot" is not your problem. Avoiding getting too cold is.

It's not that simple of a design [marsicehouse.com] - there are multiple layers, not all of them ice, and different temperature zones. It's not even pure ice, it's an ice/fiber/aerogel composite, layered onto the inside of an inflated EFTE membrane in a modified fresnel lens shape to control where the light that filters through goes. This provides the "pressure vessel" as well as radiation shielding and some degree of insulation. A person can walk around in this area without a space suit, although it's quite cold. The next shell inward is printed using just the aerogel and binder. Inside this shell it's kept warm enough for living and plant growth; basically the whole area around the living quarters is a vertical greenhouse. The innermost section, the living quarters, isn't made on Mars. It's the landing craft that contained all of the excavation/printing hardware and supplies. It's sized to be launched on a Falcon Heavy. There's basically three separate airtight shells with airlocks leaving each one (the outer ice shell, the inner aerogel shell, and the inner living quarters/spacecraft, providing a great deal of redundancy against leaks. They even did actual 3d printing prototypes with their ice composite to test its properties, and have a pretty clever concept for how to have the printer be able to climb the walls its printing (it basically uses paired wheels (upper and lower) to grab onto the ridges of the fresnel lens structure it's printing, sort of like how some roller coasters hang into their tracks.

Really, it's not that bad of a concept, IMHO. There were certainly far worse [tumblr.com] in the competition.

Why is it so hard for people to RTFA [marsicehouse.com], when it's provided in the post you're responding to?

3D Printing with Ice

Ice habitats on Earth and 3D Printing with ice are not without precedent. In consultation with our Team’s expert scientific advisors, astrophysicists, geologists, structural engineers and renowned 3D printing experts, we have achieved positive experimentation with one to one ice printing and successfully analyzed structural models.

Also, ask anybody who's served on a nuke boat in the navy, iron/steel is a far better radiation shield than water. Using (scarce) water on Mars as a radiation shield, when the entire surface is rich in iron oxide seems dumb as hell to me. You'd be better off filling bags with surface material, pressing them into blocks, and using those blocks to build igloo shaped structures. This is why most of the (decent) books about mars colonization involve living underground initially.

Not really. Earth-ram blocks are a common enough building material, and can be made by hand, or with simple tools. Instead of cement, we can use any number of masonry epoxies as a mortar, which are far easier to ship than a cement factory. Additionally, the fact that Mars has just over 1/3rd the gravitational pull as earth simplifies the building process.

all this is pretty well beside the point, because these are more of a 'long term' option, not a 'first visit'. Not like we're going to Mars any time soo

Also, ask anybody who's served on a nuke boat in the navy, iron/steel is a far better radiation shield than water.

Depends highly on the type of radiation. Iron is actually a pretty terrible shield against neutrons, for example.

As far as general purpose shielding against solar radiation and GCR, things rich in hydrogen generally are the best option. You can boost their effectiveness by borating them, especially on the inner layers, to help absorb thermal neutron secondaries.

I'm sure that some will say I'm a cynic, but if one looks at the entire history of spacefight as-imagined versus as-implemented, no functional space equipment has ever looked as sleek or smooth as the concept artists' work promised. Even the Shuttle, in its technological glory and areodynamic flight, does not look like the early prototypes of a spaceplane as envisioned by artists and dreamers.

Technology is often ugly because it is designed for function first. Form, past function, is a luxury. A nation

Is this based on anything other than being pretty and allowing NASA to have some PR?

I doubt that it's more than PR, given how they're referencing 3d printing as a hot technology right now. Mind you, NASA needs PR as it is constantly threatened with being scaled-back, but I don't think that any of these concepts would do more than influence small portions of a final engineered design.

Actually I strongly recommend that people read the design documents (linked above). While the sleek look first comes across as an architect wildly fantasizing, the shape really comes from function.

1) You have to have radiation shielding. This means massive amounts of *something*, ideally from Mars. They identify water as the easiest "something" to work with. They're probably right.

2) Gantry cranes are heavy. You don't want to ship big heavy cranes to Mars. So it's best if you can build it up from bottom to top with a small device that ascends as it makes the wall. Hence their "3d printing bot" - yes, I know 3d printing is such a buzzword, but the bot design isn't actually that complex. It prints the tracks that it drives on into the wall it's making. Hence that "rippled" look to the walls. The shape doubles as a fresnel lens to focus light, which is neat and useful - but it stems from something much simpler, the need for the wall to be climbable.

3) This approach of printing tracks into walls is easiest done if the structure is highly vertical. For simplicity, the structure is also to be printed around the landing vehicle that brings all of the hardware and materials to print the shell - the vehicle also doubling as the habitat once it's been emptied out (reuse, reuse, reuse). Rockets tend to also be highly vertically-oriented vehicles. So you get - no shock - a highly vertical structure. It's function, not style - it's just that the function happens to also be stylish.

4) So you've got an outer pressure/radiation shell and an inner vehicle to be your habitat... but obviously you have to have insulation somewhere. What's the lightest insulation you could have? Aerogel. Okay, so you're going to bring aerogel. You can't just have it on your lander's exterior, it'll burn off on entry, so it's better to print it on when you get down to the surface - after all, you've already designed and built print bots. But if you're going to spray up a wall with your robots already designed for printing shells, why not leave a gap between the lander/habitat and the aerogel insulation, giving you more useful, room-temperature space? And another gap between the insulation shell and the ice - so now you have three independent domes providing redundancy? So right there again, function dictates form - even though the resulting form looks neat.

5) So you have room-temperature space outside your lander/habitat. And you have light filtering in through aerogel and ice, since they're mostly transparent. So why not grow plants there? Hence the greenhouse - it comes at almost no cost.

So while at a first glance it just looks like some fanciful design by a wannabe art/architecture student, there's actually solid reasoning behind it. Even the size of the habitat and its payload for making the shells was dictated by existing in-development launch vehicles (designed to fit on a Falcon Heavy or SLS).

Technically, Mark Watney is the best architect on Mars. So logically, early period Martian colonial architecture would look like the parts of Fred Sanford's junkyard that didn't get blow away by a recent hurricane.

A sphere has the minimum ratio of surface area (and thus material) to volume. It's also the shape you get when you inflate the simplest shape of balloon to act as the surface you're going to print against. Modifying the ideal sphere for a number of practical constraints leads to a more domed shape as in the winning design.

Corners are also an impediment to a robot designed to ride a self-printed track around the inside of a wall, as in the design.

If you've ever tried to furnish the inside of a round room, or fill storage space with round walls, you'd know how much space is difficult to use. Making it spherical jsut makes it worse. Just because round is a natural shape does not mean anything. Crystals have a naturally rhombic elemental structure.

Actually, autonomous straight wall construction is simpler because the robot only needs to operate horizontally an vertically in the plane, then you just re-orient for each wall. Even with spherical struc

I did not say because it's a "natural" shape. I said because it's the ideal shape for maximizing internal area while reducing surface area, and it's the shape naturally reached by inflating a membrane (which is what this concept is based on). Furthermore, "internal space" != "living space". The outer shell is a pressure vessel and radiation shielding. This creates a cold but breathable and pressurized area which can function as storage space, a place for holding external equipment, an EVA prep area, etc. Th

I was not concerned with the specific construction method. I was just saying that curved walls make interior space use less efficient, and rectangular structures allow more complete use of that interior space. I honestly don't think the robotics one way or the other is going to be an issue once you've already overcome the challenge of getting to Mars. Decide what structure is best, then determine the robotics required, not the other way around.

So your basic argument is "don't worry about how hard the habitat you want to build is, just make sure that you can fit a piece of furniture anywhere in it"?

If so, I've got a wall to hit my head against.

Curved walls on the radiation shielding/pressure vessel are the best shape for the walls of a radiation-shielding pressure vessel. We're not talking about someone's bedroom here, we're talking about the thing that stops your bedroom from getting fried by high energy protons. And you want to complicate the co

So your basic argument is "don't worry about how hard the habitat you want to build is, just make sure that you can fit a piece of furniture anywhere in it"?

That is not at all what I said, that is your attempt to distort what I said to make a point. I said it makes sense to decide what structure is best first, when the building of it is not likely to be significantly more difficult either way. Your assumption that curved building is tremendously easier than straight is not one that I share with you.

I recognize that curved structures are better in general for pressure boundaries. But that implies a continuous curve and not varying ones as shown in the artist'

This is actually a pretty brilliant design, because water is easy to come by on Mars, and easier to work with than regolith or any other local material. The easiest way is to bring hydrogen from Earth, then obtain water via Sabetier reaction, using your hydrogen with CO2 from the martian atmosphere. Oxygen is the heaviest part of water, so a little bit of hydrogen goes a long way if you can get oxygen locally.

So, essentially all you need to do is create liquid water, and then deposit it and let the Martian

...It simply won't be done expensively when it can be done less expensively.

I have to agree. but what I don't understand is why build at all... DIG. Find a shelf of something similar to limestone or even thick sandstone and tunnel under it. If done properly you could have large areas supported by wrapped and bound pillars of what ever it is you are removing. Spray a humidity barrier on the walls and ceiling to keep your water from going away. Transfer excess heat to the surface and use the temperature difference to capture some electricity. The idea of growing things using sunligh

I don't disagree with having a large portion of the habitat underground, but for the long term mental health of the occupants there would need to be above-ground portions and probably portions with windows.

It will reduce the transparency. But Mars also undergoes wind scouring events - which is why Opportunity is still roving on Mars [xkcd.com] to this day.

Good transparency isn't a key aspect of the design. The basic issue is, you need radiation shielding from something, ideally something local. What's easier to work with that's local on Mars than water? Yeah, what's on Mars is really more like a salty, silty frozen muck than the pure fresh water ice that most people picture. But turning that to consistent-quality build

They certainly warrant investigation and might ultimately prove useful, but they also present about as hazardous, difficult to access terrain as one could possibly imagine. And are a total unknown at this point in time.

It does have a greenhouse built in, yes. So you could grow potatoes there (unlike the approach used in the book, which wouldn't actually work;) )

One thing that the ice house site mentions in passing, without going into the implications, is that the shape of the ice shell will act as a fresnel lens. One of the neat aspects about that is that you can have it function as basically a passive solar concentrator, boosting the effective solar constant in the greenhouse/living area..

This design does call for exactly that: bringing their own habitat and using martian materials as exterior coverings. There are three segments: the inner segment (living quarters) is the rocket that brought all of the building supplies there. It's surrounded by an aerogel dome for insulation. The ice dome for radiation shielding is outside of that. There are three separate levels of air locks in the design.

A double walled skin could be inflated with concrete foam, or polymer soil mix, in an automated system that would be very fast. The insulating properties of the foam material would then allow ice layers to be added to the external surface before a layer of soil to preserve the ice.

The concept actually kind of is what you linked to:) They inflate a dome and then spray a material that will harden onto it. The differences are that what they're spraying is water+fibers+aerogel rather than cement+water+rebar+aggregate, and the spraying is done from close range rather than long range. Bringing fibers + aerogel rather than cement + rebar is obviously a lot lighter, and the former combination gives you light (amplified in the living area by the fresnel lens shape) and increases the R-valu